In 1997 México launched its pioneering CCT program as an example of policy reform anchored in rigorous evidence. Progresa had an built-in randomized control trial to assess its impacts, which greatly contributed to: 1) policy survival across the polítical and electoral cycle; 2) program expansion driven by proven effectiveness; 3) worldwide emulation and diffusion; and 4) a significant contribution to the development of evaluation institutions in México. Paradoxically, the pioneering CCT of the 1990s has been slow to reform in reponse to key challenges of CCT programs: program graduation, social and economic inclusion, and the specific challenges of urban poverty. This paper offers an political-economy explanation of this feature and sheds some light on the evidence base that should become a part of the social policy debate for CCTS in the future.